Create a shiny module that creates a leaflet map in shiny app

Question

I have the simple shiny app below in which I create a leaflet map. I would like to create a shiny module though that would specifically create the leaflet map.

    ## app.R ##
library(shiny)
library(shinydashboard)
library(shinyWidgets)
library(leaflet)
library(dplyr)

# Some data
data<-structure(list(scientificName = c("Turdus merula Linnaeus, 1758", 
                                        "Passer domesticus (Linnaeus, 1758)", "Cantharellus cinereus (Pers.) Fr.", 
                                        "Flammulina fennae Bas", "Mycena crocata (Schrad.) P.Kumm.", 
                                        "Lepista luscina (Fr.) Singer", "Mycena permixta (Britzelm.) Sacc.", 
                                        "Rhodophyllus byssisedus (Pers.) Quel.", "Rhodophyllus porphyrophaeus (Fr.) J.E.Lange", 
                                        "Panaeolus rickenii Hora"), decimalLatitude = c(52.204429, 51.387818, 
                                                                                        52.176667, 50.066111, 49.179167, 49.419444, 52.3, 52.3, 49.419444, 
                                                                                        49.179167), decimalLongitude = c(21.189275, 19.62673, 19.088056, 
                                                                                                                         19.502778, 22.434722, 20.380556, 20.566667, 20.566667, 20.380556, 
                                                                                                                         22.434722)), row.names = c(1L, 2L, 32L, 35L, 37L, 38L, 39L, 40L, 
                                                                                                                                                    41L, 42L), class = c("spec_tbl_df", "tbl_df", "tbl", "data.frame"
                                                                                                                                                    ))
# Define the side panel UI and server
sideUI <- function(id) {
  ns <- NS(id)
  pickerInput(
    inputId = ns("sci"),
    label = "Scientific name", 
    choices = unique(data$scientificName),
    selected = unique(data$scientificName)[1] 
    
  )
  actionButton("action","Submit")
  
}

sideServer <- function(id) {
  moduleServer(
    id,
    function(input, output, session) {
      
      # define a reactive and return it
      react<-eventReactive(input$action,{
        
        omited <-subset(data, data$scientificName %in% isolate(input$sci))
      })
      return(react)
      
    })
}
# In this case this server not needed but using uiOuput/renderUI in real case
# sideServer <- function(id) { moduleServer(id,function(input, output, session) { })}

# Define the UI and server functions for the map
mapUI <- function(id) {
  ns <- NS(id)
  leafletOutput(ns("map"))
}

mapServer <- function(id, city) {
  moduleServer(
    id,
    function(input, output, session) {
      output$map<-renderLeaflet({
        
        leaflet(data = react()) %>% addTiles() %>%
          addMarkers(~decimalLatitude, ~decimalLongitude, popup = ~as.character(scientificName), label = ~as.character(scientificName))
      })
    })
}

# Build ui & server and then run
ui <- dashboardPage(
  dashboardHeader(),
  dashboardSidebar(sideUI("side")),
  dashboardBody(mapUI("mapUK"))
)
server <- function(input, output, session) {
  
  # use the reactive in another module
  city_input <- sideServer("side")
  mapServer("mapUK", city_input)
  
}
shinyApp(ui, server)

What have you tried so far? Why didn’t it work? What parts of the leaflet map should be customisable? Which of these need to change dynamically and which are fixed when the module is instantiated? You need to give us _far_ more information. (And demonstrate that you’ve made reasonable efforts of your own…’ — Limey, Jan 01 '22 at 17:17
leaflet shiny module example [here](https://stackoverflow.com/questions/69260323/how-to-use-nested-modules-with-a-leaflet-map) and links therein — user20650, Jan 01 '22 at 23:17

score 1 · Accepted Answer · answered Jan 03 '22 at 10:11

You have made some mistakes.

Below is code without these mistakes:

library(shiny)
library(shinydashboard)
library(shinyWidgets)
library(leaflet)
library(dplyr)

# Some data
data<-structure(list(scientificName = c("Turdus merula Linnaeus, 1758", 
                                        "Passer domesticus (Linnaeus, 1758)", "Cantharellus cinereus (Pers.) Fr.", 
                                        "Flammulina fennae Bas", "Mycena crocata (Schrad.) P.Kumm.", 
                                        "Lepista luscina (Fr.) Singer", "Mycena permixta (Britzelm.) Sacc.", 
                                        "Rhodophyllus byssisedus (Pers.) Quel.", "Rhodophyllus porphyrophaeus (Fr.) J.E.Lange", 
                                        "Panaeolus rickenii Hora"), decimalLatitude = c(52.204429, 51.387818, 
                                                                                        52.176667, 50.066111, 49.179167, 49.419444, 52.3, 52.3, 49.419444, 
                                                                                        49.179167), decimalLongitude = c(21.189275, 19.62673, 19.088056, 
                                                                                                                         19.502778, 22.434722, 20.380556, 20.566667, 20.566667, 20.380556, 
                                                                                                                         22.434722)), row.names = c(1L, 2L, 32L, 35L, 37L, 38L, 39L, 40L, 
                                                                                                                                                    41L, 42L), class = c("spec_tbl_df", "tbl_df", "tbl", "data.frame"
                                                                                                                                                    ))
# Define the side panel UI and server
sideUI <- function(id) {
  ns <- NS(id)
  tagList(
    pickerInput(
      inputId = ns("sci"),
      label = "Scientific name", 
      choices = unique(data$scientificName),
      selected = unique(data$scientificName)[1] 
      
    ),
    actionButton(ns("action"),"Submit")
  )
  
}

sideServer <- function(id) {
  moduleServer(
    id,
    function(input, output, session) {
      
      # define a reactive and return it
      react<-eventReactive(input$action,{
        
        omited <-subset(data, data$scientificName %in% isolate(input$sci))
      })
      
      return(react)
      
    })
}
# In this case this server not needed but using uiOuput/renderUI in real case
# sideServer <- function(id) { moduleServer(id,function(input, output, session) { })}

# Define the UI and server functions for the map
mapUI <- function(id) {
  ns <- NS(id)
  tagList(
    leafletOutput(ns("map"))
  )
}

mapServer <- function(id, city) {
  moduleServer(
    id,
    function(input, output, session) {
      output$map<-renderLeaflet({
        
        leaflet(data = city()) %>% addTiles() %>%
          addMarkers(~decimalLatitude, ~decimalLongitude, popup = ~as.character(scientificName), label = ~as.character(scientificName))
      })
    })
}

# Build ui & server and then run
ui <- dashboardPage(
  dashboardHeader(),
  dashboardSidebar(sideUI("side")),
  dashboardBody(mapUI("mapUK"))
)
server <- function(input, output, session) {
  
  # use the reactive in another module
  city_input <- sideServer("side")
  mapServer("mapUK", city_input)
  
}
shinyApp(ui, server)

Always use tagList() inside UI in modules. Sometimes it will work without it, but usually not.
In this line: actionButton(ns("action"),"Submit") you have missed ns().
In this line: leaflet(data = city()) %>% addTiles() %>% you have used react() instead of city(). That's wrong, because you don't have parameter react in your function, but city, so you have to refer to city. This is the same as in normal function, i.e. you need to refer to the parameter in function to use arguments passed to this function.

based on your solution I created this https://stackoverflow.com/questions/70565098/shiny-widget-that-is-dependent-on-other-shiny-widget-does-not-work-in-shiny-modu — firmo23, Jan 03 '22 at 11:29

Create a shiny module that creates a leaflet map in shiny app

1 Answers1